1. Field of the Invention
This invention relates to the manufacture of adhesives consisting of aminated copolymers of a vinyl compound and a vinyl compound having at least one epoxy group.
2. Description of the Prior Art
In recent times, significant use has been made of polyvinylfluoride sheets for laminated structures which, for example, are used as wall covering materials since they have superior weather resistance, wear resistance and solvent resistance. The polyvinylfluoride sheets are marketed under the trade name "Tedlar" by E. I. duPont de Nemours & Co. In the polyvinylfluoride polymer, one hydrogen atom is substituted by one fluorine atom for each ethylene unit of polyethylene. An adhesive to be used for attaching the "Tedlar" film or sheet to the surface of a metal such as aluminum must have various requirements, for example, it should have high adhesiveness, high cohesiveness, a stability to hydrolysis and the like. If the adhesive does not meet these requirements, the film or sheet is apt to be peeled from the surface of the metal, and the polyvinylfluoride cannot be used effectively.
Adhesives for "Tedlar" film or sheet materials are disclosed in Japanese Patent Official Gazettes No. 18530/1963, (corresponding to U.S. Pat. No. 3,133,854), No. 26763/1963 and No. 11918/1967 to E. I. duPont de Nemours & Co. These adhesives are manufactured in a process in which one or more types of (meth)acrylates are copolymerized with a small amount of a monomer having an epoxy group, and gaseous ammonia or a primary monoamine are reacted with the resulting copolymer. The adhesive thus obtained consists of a (meth)acrylate polymer having an amino group or an imino group on the side chain.
The "Tedlar" film to be attached to the substrate may also be surface treated in a special manner as described in Japanese Patent Official Gazettes No. 18530/1963 and 11918/1967. We have investigated the adhesive properties of the surface treated "Tedlar" produced according to these disclosures. An (meth)acrylic polymer having a carboxyl group, a hydroxyl group, and amide group or a carbonyl group as functional groups on the side chain exhibited little adhesiveness to the "Tedlar." An (meth)acrylic polymer having glycidyl groups at the side chain exhibited some adhesiveness to the "Tedlar." However, such adhesiveness was not particularly satisfactory.
In the manufacture of the above described adhesives, gaseous ammonia is fed into an autoclave containing the copolymer under pressures on the order of 10 Kg/cm.sup.2 for a long time such as 12 hours to cause the ammonia to react with the copolymer. Such manufacturing methods have the disadvantage that they require a special reaction vessel which is resistive to the pressure conditions, and which can handle gaseous ammonia. Furthermore, after the end of the reaction, the interior of the reaction vessel has to be put under a relatively low pressure such as 100 mmHg by a vacuum pump to discharge the remaining ammonia gas.